Serbia partially accepted the ultimatum from Austria-Hungary but rejected some of the demands. This led to Austria-Hungary declaring war on Serbia, which ultimately sparked the beginning of World War I.
Austria sent the ultimatum to Serbia on July 23rd 1914
Serbia
When Serbia responded to Austria-Hungary's ultimatum, they accepted all the conditions save one. Austria-Hungary immediately declared war on Serbia, which had always been their intention given the demeaning demands they had made.
23rd July 1914
Because the the Archduke Franze Ferdinand was the heir to the Austria-Hungary throne when him and his wife when assassinated by a Serbian Nationalist in Sarejevo. Austria Hungry Gave Serbia a ultimatum and when Serbia did not follow the ultimatum Austria-Hungry declared war with Serbia
Austria-Hungary did not directly give anything to Serbia during World War I; rather, the conflict was sparked by tensions between the two nations. The assassination of Archduke Franz Ferdinand of Austria in June 1914 by a Bosnian Serb nationalist led Austria-Hungary to issue an ultimatum to Serbia. When Serbia's response was deemed unsatisfactory, Austria-Hungary declared war on Serbia, initiating the larger conflict of World War I.
The outbreak of World War I was triggered by a series of events involving Austria-Hungary, Serbia, and Russia. After the assassination of Archduke Franz Ferdinand of Austria by a Serbian nationalist in June 1914, Austria-Hungary issued an ultimatum to Serbia with harsh demands. Serbia's response was deemed unsatisfactory, prompting Austria-Hungary to declare war on Serbia on July 28, 1914. Russia, in defense of Serbia and its Slavic allies, began mobilizing its army, which escalated tensions and led to the broader conflict involving multiple nations.
I am guessing that this question is referring to the Ultimatum given by the Austria-Hungarian government to Serbia just before WW1. The whole point of the conflict between Serbia and Austria at the time was a conflict between Russia and Austra fighting for allegiance of the strongest country in the Balkans, and Serbia feeling threatend in its sovereignty. The ultimatum was in a form which was apparent to everyone that Serbia could not accept, since the political consequences of agreeing to it and loosing a war were the same.
Germany could have refused to back Austria on the grounds that the ultimatum to Serbia was too harsh. ;)
In July 1914, Austria-Hungary issued an ultimatum to Serbia containing ten demands, with the most critical ones requiring Serbia to suppress anti-Austrian propaganda and allow Austro-Hungarian officials to participate in the investigation of the assassination of Archduke Franz Ferdinand. The ultimatum was deliberately harsh, aiming to provoke a conflict. Serbia accepted most of the demands but rejected some key points, leading Austria-Hungary to declare war on Serbia on July 28, 1914, which ultimately escalated into World War I.
Austria-Hungary issued an ultimatum to Serbia on July 23, 1914, following the assassination of Archduke Franz Ferdinand. The ultimatum contained要求 that aimed to limit Serbia's sovereignty, including allowing Austrian officials to participate in the investigation of the assassination. Serbia accepted most of the demands but rejected a few, leading Austria-Hungary to declare war on Serbia on July 28, 1914, which ultimately escalated into World War I.